Properties and Microstructure of Low-Strength Recycled Concrete Aggregate Treated Using Cement–Fly Ash Slurry with Various Concentrations and Soaking Durations
Publication: Journal of Materials in Civil Engineering
Volume 36, Issue 10
Abstract
Utilizing recycled concrete aggregate (RCA) is a countermeasure to address the scarcity of landfills and the depletion of natural aggregates. Surface modification techniques have been proposed and implemented to improve the properties of RCA; however, to our best knowledge, few investigations on improving RCA under various pozzolanic slurry concentrations and extended soaking durations have been done. This study comprehensively assessed the properties and microstructure of low-strength RCA treated with cement–fly ash slurry with different concentrations and soaking durations. The purposes of this study were not only to provide the optimal slurry concentration and treatment duration but also to explore the enhancement mechanism of RCA under various treatment conditions. The RCA from concrete with a low-strength grade of 20 MPa was soaked in cement–fly ash slurry at low and high concentrations (i.e., 30% and 70% by mass of RCA, respectively) for 24 and 72 h. The physical and mechanical properties of RCA before and after treatment were evaluated through water absorption and crushing value measurements, respectively. Additionally, the pore structure, contents, surface morphology, and phase compositions of RCAs were evaluated through a mercury intrusion porosimetry test, thermal gravimetric differential thermal analysis (TG-DTA), scanning electron microscopy, and X-ray diffraction (XRD) analyses, respectively. The water absorption of treated RCA reduced by 9.2%–37.9%, whereas the crushing value decreased by 8.6%–26.9% compared with the untreated RCA. The TG-DTA results indicated a 22.3%–43.8% increase in the content of treated RCA. The XRD analysis depicted a higher ettringite (AFt) peak in all treated RCA samples compared with the untreated sample. For both concentrations, with a 24 h treatment, the slurry infiltration effect was clearly observable, whereas the 72 h treatment resulted in the formation of a pozzolanic coating layer on the RCA surface. In conclusion, the optimal slurry concentration and soaking duration were 70% and 72 h, respectively.
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Data Availability Statement
All data, models, and code generated or used during the study appear in the published article.
Acknowledgments
We acknowledge Ho Chi Minh City University of Technology (HCMUT), VNU-HCM for supporting this study.
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Published In
Journal of Materials in Civil Engineering
Volume 36 • Issue 10 • October 2024
Copyright
© 2024 American Society of Civil Engineers.
History
Received: Nov 7, 2023
Accepted: Mar 12, 2024
Published online: Jul 24, 2024
Published in print: Oct 1, 2024
Discussion open until: Dec 24, 2024
ASCE Technical Topics:
- Aggregates
- Analysis (by type)
- Ashes
- Cement
- Concrete
- Engineering fundamentals
- Engineering materials (by type)
- Engineering mechanics
- Environmental engineering
- Infrastructure
- Materials characterization
- Materials engineering
- Microstructure
- Pavements
- Thermal analysis
- Thermodynamics
- Transportation engineering
- Water treatment
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